UPDATE Aug. 23 – 9:30am CDT:From airfare analyst Rick Seaney: ” A short time ago, American Airlines began pulling out of the airfare hike attempt, which is typically a sign of mass rollbacks to come.”

UPDATE Aug. 23 – 8:30am CDT: According to airfare analyst Rick Seaney, “The legacy airlines have been matching this hike attempt, while Southwest remains sitting on the sidelines; no signs of a rollback just yet.”

The earlier hike attempt, which was successful, covered routes less than 500 miles long such as New York to Pittsburgh. United’s current hike attempt includes longer routes, including New York to Chicago.

Airfare analyst and FareCompare co-founder Rick Seaney said, “United appears to be probing other airlines’ appetite for further hikes, especially after the swift matching that followed Southwest’s hike last Friday.” Seaney added that recent airfare hiking activity belies any nervousness airlines may be having about fall demand.

The last successful broad increase was over a month ago when United successfully raised prices on July 20. More recent hike attempts have met with limited success.